The present invention broadly concerns read/write electronic devices wherein a tape is used for recording or retrieving data. Specifically, the present invention concerns guides that facilitate packing of tape onto a take-up hub. The guide according to the present invention may be used with such electronic device or incorporated into tape cartridges. The device is particularly directed to prevent misregistration of the tape that is caused by air entrainment.
Tape media are used to store data in a compact and accessible manner. Typically, this has been accomplished by winding the elongated strip of tape onto a reel. Typically, such reels are constructed to have a central hub that has annular flanges and a width slightly greater than the width of the tape. It is also known to use flangeless hubs in winding tape media. In either case, the hub is rotated about a central winding axis, and the length of tape is wrapped circumferentially around the hub. Such winding results in a tape pack as successive layers of tape build in a radial direction. The edges of the tape generally define a pair of oppositely disposed surfaces generally along planes that are perpendicular to the winding axis; the width of the tape pack is thus defined by the distance between these two planes. The flanges of a flanged reel are intended to protect the tape pack.
Storage reels of tape, whether flanged or flangeless (for example as used in cartridges) may be placed on the machine during use. The length of the tape is then passed through the machine so that information may be placed on the tape or retrieved therefrom. During this process, the length of tape is transferred onto a take-up reel or hub that is either a part of the machine itself, included within the cartridge or that is mounted and demounted from such machine. After being transported through the machine, the tape may be rewound onto the storage reel and removed from the machine.
In the beginning, the speeds associated with the transfer of tape between the storage reel and the take-up reel were relatively slow. The registration of the edges of the tape layers to form the opposite surfaces of the tape pack was not especially critical. Often, the edges of consecutive layers of the tape might be slightly off-set from one another or xe2x80x9cstagger-wrappedxe2x80x9d. Such was the case for both magnetic recording tape and tapes used, for example, in the motion picture industry (where a series of photographic images are placed consecutively on the tape medium).
In more recent times, the speed of wrapping or winding a tape onto either the storage reel or the take-up reel has increased dramatically. This is especially true in the electronic information storage arena wherein magnetic tape, or xe2x80x9cfilmxe2x80x9d or optical tape is used to store data, both for on-line usage as well as for archival purposes. In such electronic devices, a magnetic coil is used as a transducer to imprint data magnetically on a moving band of magnetic film; thereafter, when the film is advanced across the transducer, the data may be accessed. The ability to write data rapidly onto a film and the accessibility of data to be read from the film is a function of two variables: (1) the density of storage; and (2) the speed at which the tape medium may be transported across and accurately written/read by the transducer.
As was explained in my earlier U.S. Pat. No. 5,777,823, issued Jul. 7, 1998, it is important that the lateral edge of the tape moving in a transport direction be properly registered along a reference plane, called the datum, so that the data may be accurately input and retrieved from the tape medium. Support of the tape during transport is therefore critical, and typically employs guide rollers, air bearing and the like as is known in the art.
As tape transport speeds have increased, a problem has evolved which is interchangeably called xe2x80x9cscatterwindxe2x80x9d or xe2x80x9cstagger-wrapxe2x80x9d. Where tape is wound at high speed onto a hub, the tape entrains air. That is, air within the boundary of air adjacent to the tape moves into the tape pack and becomes entrapped between the advancing layer and those layers already on the tape pack. Some of this converging wedge of air is laterally displaced at the xe2x80x9cnipxe2x80x9d which is the point of tangency between the film pack and the incoming (or outgoing) layer of tape. Despite this displacement, a significant portion of the air is nonetheless trapped between the layers of the film pack such that the radial outward layers of the tape pack float slightly with respect to one another because they are separated by the spiral-air bearing created by the self-pressurized air film.
When the tape pack is subsequently brought to rest, the spiral-air bearing is ejected so as to decrease the pack""s radius until all adjacent tape layers have come into direct contact. As this occurs, the layers may shift laterally with respect to one another resulting in a tape pack that has a significant amount of stagger wrap. Indeed, at the present time, there can be as much as 0.010 to 0.040 (about 0.25 mm to 1.0 mm) stagger between adjacent tape edges.
Stagger-wrap presents a problem to the industry where the alignment of the lateral edge of the tape is critical with the read/write transducer. If a tape pack has a significant amount of stagger wrap, the perturbation of this stagger wrap propagates through the advancing tape layer as it is played off of the reel or hub. This causes potential error in either reading or writing the data. Therefore, it is desirable to eliminate the misregistration of the layers forming the tape pack by guiding the registration of the incoming tape layer as it winds onto the hub.
As should be appreciated, when tape is wound between a take-up reel and a storage reel, it is necessarily under a physical tension xe2x80x9cTxe2x80x9d. The force required to displace a tape of length xe2x80x9cLxe2x80x9d through a misregistration xe2x80x9cdxe2x80x9d is given by equation: F=Td/L. By maximizing the length an minimizing misregistration, forces on the tape will be minimal subjecting the tape to the smallest and gentlest guiding force.
Others have recognized the air entrainment problem of high speed winding, and attempts have been made to address this problem. A general discussion of the air entrainment issue is discussed, for example, in M. B. Keshaven and J. A. Wickert, xe2x80x9cTransient Discharge of Entrained Air from Wound Rollxe2x80x9d, Transactions of the ASME, Vol. 65, 804-805 (December 1988) and in M. B. Keshaven and J. A. Wickert, xe2x80x9cAir Entrainment During Study-State Web Windingxe2x80x9d, Transactions of the ASME, Vol. 64, pages 916-917 (December 1997).
In U.S. Pat. No. 6,045,086 to Jeans, issued Apr. 4, 2000, a background discussion is set forth which describes various techniques employed in an attempt to reduce the stagger wrap or scatterwind. As explained in the ""086 Patent, previous attempts at neatly packing a film onto a film pack include the use of self-packing glass reels, liner sheets, magnetic forces and mechanical forces. In the first Keshaven et al article noted above, the use of packing or xe2x80x9clay-on rollersxe2x80x9d or drive belts that preload the tape against the roll have been used. However, those solutions can deform the tape. Moreover, the fragility of the thinner recording media and next-generation systems may effectively preclude the use of such mechanical means to reduce the thickness of the entrained air film.
Of the techniques noted above, self-packing glass reels are precision tape reels wherein the flanges are formed of glass. The flanges are slightly radially converging so that the decreased spacing of the flanges constrains lateral motion of the tape. These glass reels are high priced and require precise alignment or other guide elements in the tape path. In addition, the use of such self-packing glass reels do not eliminate the inertia of the flanged reels during acceleration and deceleration of the tape take-up and storage reels.
Magnetic winding devices rely on magnetic fields to align the film. This works only on magnetic films and is not possible to use to optical films. Mechanical forces from pulleys or rollers are used to urge the film into registration as it would onto the tape pack. However, these mechanical devices apply high radial pressure to the film to squeeze out air, and can damage the film by the mechanical contact therewith.
These problems were addressed in the ""086 Patent mentioned above. The ""086 Patent discloses a method and apparatus for rewinding a film to reduce scatter winds. The film packing guide is structured as a flexible sheet of elastic material that extends radially of the tape pack and is canted at an acute angle to a surface defined by the respective edges fo the tape layers forming the tape pack. Thus, the elastic packing guide contacts the circumferential edge of the outer most tape layer at a location displaced downstream of the nip.
Despite the advantages provided by prior art structures, there remains a need for improved tape packing guides and apparatus that are operative to wind a tape medium with reduced misregistration for play and storage. Moreover, there is a need to provide improved packing guides that place less stress on the tape medium during motion. The present invention is directed to providing such improved structure and apparatus which can be incorporated of a tape system, as part of a take-up or storage reel and as tape storage cassettes.
Accordingly, there remains a need to provide new and improved take-up and storage devices for data. There is a continued need for devices that can read and write tape film at increasingly higher speeds. There is a further need for storage and take up hubs that are packed with reduced misalignment of the tape layers thus avoiding stagger-wrap. The present invention is directed to meeting these needs.
It is an object of the present invention to provide a new and useful structure which can be incorporated into a tape drive system or which can be formed as a tape reel or cartridge that reduces the misregistration of the stagger-wrap as the tape is wound into a tape pack.
It is another object of the present invention to provide an apparatus that includes a rigid packing arm that more precisely registers a link of tape incoming onto a tape pack to reduce the stagger wrap thereof, especially where the rigid packing arm is biased against the tape pack.
It is yet another object of the present invention is to provide apparatus including a packing arm that more precisely registers a link of tape incoming onto a tape pack to reduce the stagger wrap thereof while employing a low magnitude force on the tape.
Yet a further object of the present invention is to provide a packing guide that helps register a tape as it is wound onto a tape pack and which concurrently removes light burrs resulting from the slitting process and also lightly burnishes the tape edge.
According to the present invention, then, an apparatus is provided to wind a tape medium relative to a frame structure so that the tape medium is wound into a tape pack with reduced misregistration for play and storage. Broadly, this apparatus includes a hub that is supported by the frame structure and that is operative to wrappingly receive the tape medium. A drive engages the hub and selectively rotates the hub about a wind axis so that the length of the tape medium is wound thereon to form a spool-like tape pack. This tape pack has a pair of oppositely disposed surfaces defined by edges of the registered layers forming the tape pack. The apparatus according to the present invention includes a rigid packing arm that has a proximal end portion that is disposed proximately to the hub and that extends longitudinally from the hub to a distal end portion located at the circumference of the tape pack. The packing arm has a contact surface that is operative to contact a first surface of the tape pack. A support member supports the packing arm in contact with the first surface of the tape pack.
The packing arm can have an arcuate configuration or it can be linear, but, in either case, it should contact the first surface of the tape pack at a location adjacent to the nip. Here, also, the contact surface of the packing arm may be provided with a longitudinally extending groove that is located between the distal end portion and the proximal end portion of the packing arm. This groove allows air to laterally bleed at the nip region so as to achieve a better tape pack. The distal end portion of the packing arm preferably overlaps the hub and, if desired, is resiliently biased and in contact with the surface of the tape pack. Biasing may be accomplished by an elastomeric material or, alternatively, a spring, such as a leaf spring. The packing arm is preferably constructed of a nonferrous material, such as a ceramic, and the contact surface is highly polished.
Preferably, there are a plurality of rigid packing arms associated with each hub. Each of the packing arms thus includes a proximal end portion located at the hub and extending longitudinally from the hub to a distal end portion at the circumference at the tape pack. The packing arms are preferably disposed equiangularly about the wind axis. The packing arms are oriented such that at least one of the packing arms always contacts the first surface adjacent to the nip as the tape pack is wound. Here, again, each packing arm may be provided with a longitudinal groove. Alternatively, the tape pack may be sandwiched between a pair of opposed rigid packing arms.
While the packing arms can be arcuate in configuration, it is important that each packing arm has a radial length that is greater than its circumferential length. The hub may be disposed in a cartridge housing that is mountable and demountable relative to the frame structure. Where a cartridge is used, the packing arm is mounted to the cartridge housing.
The present invention also contemplates a tape reel assembly, such as a cartridge, that is adapted to be mounted to and demounted from a tape drive apparatus for winding a tape medium therein. Here, the tape reel assembly includes a housing and a hub rotatably disposed in the housing. This hub is again operative to wrappingly receive the tape medium thereon to form a spool-like tape pack with a portion of the tape medium contacting the tape pack at the tangential nip. A packing arm is disposed in the housing and includes a proximal end portion at the hub and extends longitudinally from the hub to a distal end portion at the circumference of the tape pack. This packing arm again has a contact surface operative to contact the first surface of the tape pack. The packing arm can be constructed as described above and there can be a pair of opposed packing arms or a plurality of packing arms equiangularly disposed about the wind axis. Here, it is preferred that the hub be a flangeless hub.
It should be understood that the present invention provides an improvement to a tape drive system wherein the tape drive system typically has a frame, a read/write head disposed on the frame, first and second winding members each disposed on the frame and adapted so that a tape medium may be selectively wound thereon and unwound therefrom to form a respective tape pack. A tape support structure is disposed on the frame and is operative to support a tape for transport between the first and second winding members and across the read/write head. First and second drives are each operative to rotate the first and second winding members, respectively. The improvement thus includes a rigid packing arm having a proximal end portion located proximally to an outer edge of at least one of the winding members and extending from the outer edge to a distal end portion at the circumference of the tape pack. The packing arm has a contact surface operative to contact the first surface of a respective tape pack, and a support member is employed to support the packing arm in contact with the first surface of the respective tape pack. Here, again, the packing arm may be constructed as described above.
These and other objects of the present invention will become more readily appreciated and understood from a consideration of the following detailed description of the exemplary embodiments of the present invention when taken together with the accompanying drawings, in which: